package project1;
import java.util.Scanner;
public class text3 {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		System.out.println("s");
		double s = input.nextDouble();
		double area = s*s*(3*Math.pow(3,0.5)/2);
		/*Math.pow(a,b)  b=0.5表示*/
		System.out.println(area);
		/*s=边长     //area=面积*/
	}

}
